Battery charging from Alternator

Is the charge controller the voltage regulator?

Hi Alex

No - not car volts regular.

Really need more details on your dual battery setup, it could be straight connection ( parallel to main battery) . In which case it will never fully charge

Or voltage senstitive relay type e.g. redarc - unlikely to get to 100% but will get a fair way in a few hours

Or a setup voltage charge controller e.g. arrid - probably take 2-3 hours and is only type capable of 100% in less than a full days drive

Robin Miller

Thanks for the info. Out of interest, what's the relationship between SoC, total battery capacity and time to rechange.

For example: if a 100ah battery at 50% SoC takes 3 hours to get back to 95% SoC, would a 200ah battery at 50% SoC take 6 hours to get back to 95% SoC or could the alternator provide more current to maintain a 3 hr change time?

Hi again Alex, depending on the type of battery(s) and the size of your alternator, the charging time should be roughly the same for 100 A/H and 200 A/H for the average alternator. Anything much bigger than 200 A/H will then depend on just how big your alternator is.

Remember, these are all rough figures because there are a number of factors that can effect charging of any batteries so this info is very generalised but a standard 100 amp wet cell battery with about 50% SoC will probably pull about 20 amps MAXIMUM, initially and as the battery charges, the current will drop and a 200 amp wet cell or 2 x 100 amp wet cells in parallel will pull at MAXIMUM around 40 amps.

AGMs may in fact NOT draw as much initially but will draw the same current constantly till they are near fully charged and even this can vary greatly between brands.

Now this should get a whole host of arguments going but as I stated at the beginning, this is a generalisation and for a starter, no charging voltage level is mentioned. This in itself, is the single most important factor when working out the charging time of any battery, so the figures posted above are just basic instances.

Alex, you will need a lot more info relating to your own set-up to be able to get a far more accurate idea of charging times required.

Cheers.